Over the last decade, a number of studies at the Georgia Institute of Technology (GT) have evaluated the thermal hydraulics of the design of the helium-cooled modular divertor with multiple jets (HEMJ) originally developed at the Karlsruhe Institute of Technology. Using the GT helium loop, a test section of a single HEMJ finger heated by a radio-frequency (rf) induction heater was studied at near prototypical condition at pressures of ~10 MPa, maximum mass flow rates of 8 g/s, and maximum helium inlet temperatures Ti of 425°C. The area-averaged cooled surface temperature was estimated from embedded thermocouple measurements. This, together with the average incident heat flux , was used to determine the average heat transfer coefficient and the corresponding Nusselt number over the cooled surface. The normalized pressure loss coefficient KL was determined from the pressure drop measured across the test section.

The helium loop was modified last year by enclosing the test section and heater within an argon-filled stainless steel chamber to minimize oxidation of the tungsten-alloy test section. Initial results, when extrapolated to prototypical conditions, suggested that was about 20% higher than our previous results. However, the maximum heat flux for these results was less than 3 MW/m2 due to rf coupling with the steel chamber walls. The chamber was then recently upgraded to a glass–stainless steel enclosure with modified feedthroughs for the induction heater connections to minimize this coupling. With this upgrade, a maximum incident heat flux  = 8.1 MW/m2 was achieved. This work presents experimental estimates and correlations for and KL at higher heat fluxes. These results provide greater confidence when estimating the maximum heat flux that can be accommodated by the HEMJ at fully prototypical conditions.

Finally, preliminary metrology results for the test section used to experimentally study the simplified flat design variant of the HEMJ are presented as part of an effort to resolve recently reported discrepancies between experimentally estimated and numerically simulated